1. Field of the Invention
The described technology relates generally to a display device. More particularly, the described technology relates generally to a display device mounted with an integrated circuit chip.
2. Description of the Related Art
As a display device for displaying images, an organic light emitting diode (OLED) display has recently been spotlighted.
The OLED display has self-luminance characteristics, and the thickness and weight thereof can be reduced since a separate light source is not required, unlike a liquid crystal display (LCD). In addition, the OLED display has high-quality characteristics such as low power consumption, high luminance, fast reaction time, and the like.
In a display device such as the organic light emitting diode (OLED) display, an element is formed on a substrate made of a material such as glass or plastic to manufacture the display device, and an integrated circuit chip for generating various signals to operate the display device may be mounted at a predetermined region of the substrate where the display device is formed. Here, the integrated circuit chip may be divided into a chip on glass (COG) or a chip on flexible printed circuit board (FPCB) (COF) according to the mounting position. Here, COG means a type in which the integrated circuit chip is mounted on the substrate, and COF means a type in which the integrated circuit chip is mounted on a film such as a polyimide film for the FPCB.
Among them, in the case of the COG in which the integrated circuit chip is mounted on the substrate, an anisotropic conductive film (ACF) is interposed between a pad formed in the substrate and the terminal of the integrated circuit chip, and the integrated circuit chip is mounted on the substrate. Here, a direct connection between the pad of the substrate and the terminal of the integrated circuit chip is realized by conductive balls included in the anisotropic conductive film, and adhesion between the substrate and the integrated circuit chip is realized by an adhesive layer enclosing the conductive balls included in the anisotropic conductive film. The conductive balls are compressed between the pad of the substrate and the terminal of the integrated circuit chip, and the conductive balls have excellent elastic restoring force such that the contact area between the pad and the terminal is increased by the pressure applied by the pad and the terminal, such that the contact resistance between the conductive balls and the pad, and the conductive balls and the terminal, is decreased according to an increase of the pressure applied to the conductive balls.
However, when pressure of more than a predetermined amount is applied to the conductive balls, the elastic restoring force of the compressed conductive halls exceeds the fixing capacity limit of the adhesive layer executing the adhesion between the substrate and the integrated circuit chip such that the adhesive layer does, not maintain the compressed shape of the conductive balls, and thereby the shape of the conductive balls is restored, and accordingly the contact resistance between the conductive balls and the pad, and the conductive balls and the terminal, is increased.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.